1. Field of the Invention
The present invention relates to a crosslinked polyvinyl alcohol gel which is used for a gel chromatography.
More particularly, it relates to a crosslinked polyvinyl alcohol gel obtained by copolymerizing vinyl acylate and a crosslinking agent having triazine ring and hydrolyzing the product.
2. Description of the Prior Art
The gel chromatography is the newest chromatography using a porous gel as a packing to separate compounds depending upon sizes of the molecules as well-known.
The gel chromatography can be applied for an aqueous solution or an organic solvent solution in various fields and can be applied for most of the compounds having different molecular weight. Thus, the gel chromatography can be a filtering technology which can be industrially applied in various fields.
As packing gels used in a gel chromatography in an aqueous solution, dextran gel and polyacrylamide gel are mainly used and also other gels such as starch gel, agar gel and agarose gel have been used.
However, these conventional packing gels used in the aqueous solution, soften as a function of increasing pore size as a results of water content, whereby the packed gel easily pulverizes when subjected to such mechanical operations as stirring when packed in a column etc. and it has sufficient strength to be durable in pressurizing operations, disadvantageously. That is, the pulverizing of the packed gel causes nonuniform packing in the column to deteriorate the separating characteristics.
Thus, the conventional gels for aqueous gel chromatography is difficult to be uniformly packed in a large column. This is one of the reasons for preventing an industrial application of the aqueous gel chromatography.
Such disadvantages of the conventional aqueous gels have been caused because the gels have only small pore size in a dry condition and have large pore size by swelling in an aqueous solution and the difference of the pore sizes in the dry condition and in the wet condition is too large.
In order to overcome these disadvantages, it is necessary to increase a strength in the crosslinked form and to have the same pore size in the dry condition as the pore size in an aqueous solution.
The present invention has been attained by studying crosslinking agents for gels used in aqueous solutions. It is to improve the strength of the gels used in aqueous solutions and to use the gel as a packing for a gel chromatography. The gel is used for effectively desalting from an aqueous solution of a macromolecular compound.
The product of the present invention used for desalting from an aqueous solution of a macromolecular compound is produced by using polyvinyl alcohol gel crosslinked by a crosslinking agent having triazine ring such as triallyl isocyanurate.
It has been well-known that a polyvinyl alcohol gel has molecular weight fractioning characteristics as a gel packed in an aqueous gel chromatography. For example, it has been proposed to use the polyvinyl alcohol gel obtained by hydrolyzing polyvinyl acetate crosslinked with butanedioldivinyl ether by W. Heitz in Macromolekularen Chemie 98 42 (1966). It has been also proposed to produce a polyvinyl alcohol gel by hydrolyzing a copolymer of vinyl acetate and diethyleneglycol dimethacrylate with a base and then, post-crosslinking the product with epichlorohydrin in Japanese Unexamined Patent Publication No. 138077/1977.
However, as is well-known, these crosslinking agents such as diethyleneglycol dimethacrylate and butanediol divinyl ether cause hydrolysis of the crosslinking agents at the hydrolysis of the polyvinyl acetate. Thus, it is difficult to maintain the desired initial crosslinkage.
It has been proposed to carry out the post-crosslinking treatment with epichlorohydrin after the hydrolysis of polyvinyl acetate from said view-point in Japanese Unexamined Patent Publication No. 138077/1977.